The Standard Template Library for Extra Large Data Sets (STXXL) is
here.
Some notes are also available explaining
how to install STXXL on a Linux system, and run a test program.

Software (unix C programs, in a
.tar file) for
converting between geographical coordinates and
Universal Transverse Mercator (UTM) coordinates.
The
readme.txt file is
helpful in understanding how the software works.

The
TPIE
(Templated Portable I/O Environment) library is a tool box
providing efficient and convenient tools to ease the implementation of
algorithms and data structures on very large sets of data. It is
currently being maintained at
MADALGO (thanks Thomas).

Dia is a diagram creation
program for Linux, MacOS X and Windows. It is open source, and is a great
tool for design of software using UML. It can also be used to draw many
other types of software design diagrams (e.g. entity relationship,
flowcharts). Dia is released under the
GNU General Public License, version 2.